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International Calendar
The International Calendar is based upon the rules laid out in the international standard ISO 8601. It actually consists of a primary calendar, which defines a year based on months and a leap day rule (Gregorian calendar), and a secondary calendar, which uses the same year count but subdivides a year into weeks. A modest way to propose calendar reforms are incremental, backwards-compatible additions and clarifications to this standard. Several such enhancements are possible, some of which are furthermore compatible with alternate calendar proposals, i.e. the International Calendar is a superset thereof. It is a best practice accepted in standardization to collect existing use deviating from the current standard, analyze it and, finally, form rules based upon the findings, which are compatible as much as possible with both the existing standards and popular habits. There is, for instance, much precedent in labeling quarters of a year “Q1” through “Q4”, although the exact definition of a quarter varies. It is also common to speak of the n''th week of a month, but the standard currently only implicitly defines a rule for that by prescribing which year a week belongs to. It is also common to speak of the ''n''th (instance of a) weekday in a month. Especially for some religious and esoteric purposes, the solstices and equinoxes (including visibility of constellations) or the phases of the moon are more relevant than months and weeks. It may make sense to define notation for auxiliary years based on that, aligned with the common year count. The seven-day week cycle is important to several religious groups and therefore is hard to break apart from, see the failed attempt to introduce the World Calendar by the United Nations in the 1950s. In financial contexts, the month and year are often simplified to 30 and 360 days, respectively. Guidelines * The ''extended format becomes the standard format, the'' basic format'' is a condensed or collapsed or compact version thereof. * Do not add ambiguous formats. * Only add a redundant format if there are very good reasons for it. * Collapse everything or nothing. * Support condensed format where possible. ** Do not condense formats with a one-digt part, except when it is the last one and follows an alphabetic marker. (This is a suggestion that this page does not yet adhere to.) ** Do not condense formats with plus or minus sign before the year number. * Do not support two-digit years in new formats, but consider their existence. ** Assume centuries for two digits in isolation. * Extend existing schemes and conventions. ** Apply week of year determination rule to months, quarters etc. ** Reuse the ‘W’ convention for other entities if necessary. * Do not break the week cycle. * Stay with 97/400 leap year cycle, change 4–100–400 rule for all or no calendar. * Partial values on the right may be left out. This specifies less specific dates. * Partial values on the left may be left out without dropping separators and markers. Missing parts are implied (usually using the live value). ** Separators may be dropped if markers alone make the format unambiguous. * Single alphabetic letters in a format are called “markers”. * Do not support years with more than ten digits which is already more than than the age of the universe. * Dates are ordinal, except for the year, but times are rational, i.e. the former start at 1, the latter begin with 0. Agenda * Introduce wildcard characters for fields, e.g. ‘*’, and single digits, e.g. ‘?’, ‘_’ or ‘X’. * Specify file system and URI path coding of dates using the slash instead of the hyphen as field separator. * Write a formal grammar for parsers/lexers. Existing formats Note that implied century was possible in ISO 8601:2000, but this truncated format was removed in the third edition, ISO 8601:2004. For backwards compatibility, however, CCYYMM instead of YYMMDD is invalid. From here on, the identifier ±CCYY (±4) refers to any of the three 4-digit formats above. General clarifications, additions or enhancements Large years * Numeric dates * ‘+’ or ‘-’ prefix ±CCYYMM (with leading plus or minus sign) could be confused with six-digit years ±CCCCYY, seven-digit and eight-digit years would be ambiguous with the condensed ±CCYYDDD ordinal dates and ±CCYYMMDD full dates, respectively. Therefore compact formats are only valid without a leading plus or minus sign unless they contain a marker as first character after the year. Note, that the deprecated YYDDD is already compatible with five-digit years ±CCCYY (i.e. almost all of human history). Four-digit years should not have a preceding plus sign to avoid ambiguity. The characters minus sign U+2212 ‘−’ and en dash U+2012 ‘–’ are also valid instead of hyphen-minus U+002D ‘-’ before years. They are invalid as a separator. Month-based additions and clarifications Triad: 3-month quarters Three consecutive months make one of four triads. They are 90 (91 with Feb29), 91, 92 and 92 days long, respectively, and align with the common year, not with week dates. These should not be subdivided into weeks. The condensed format without hyphens is not supported with these dates, because they would collide with existing ones. Weekday of month or of triad this subsection is optional * Numeric dates The n''th weekday of a triad or month may be specified by leaving out the ‘W’ marker of either format. Note that the -Q-01-1–7 and -MM-1-1–7 formats do not denote partial weeks but the first seven days of a triad or month, respectively, which often belong to two different weeks, therefore the D part is never optional, i.e. -Q-WW (which would be ambiguous with -Q-DD) and -MM-W are invalid, and, like their bases, the formats cannot be condensed. Week-based additions The '''week year' used herein has exactly 52 weeks (364 days) in a short year or 53 weeks (371 days) in a long year as opposed to the month year without ‘W’ marker which has 365 days in a common year or 366 days in a leap year. The term normal year is ambiguous, as it means a short year in the context of week years and a common year in the context of month years. Quart: 13-week quarters * Alphanumeric dates * ‘Q’ marker Each of the 4 quarters, called quarts, has 13 weeks excatly, except for the final one in long years. This long quart has 14 weeks then. Although there is no consensus on how quarts of 91 days or 13 weeks should be separated into 3 months of almost equal length, there are just two basic approaches: one divides each quarter into portions of 30 days twice and 31 days once, the other uses 4 weeks twice and 5 weeks once. Choosing the former, the Common-Civil-Calendar-and-Time calendar, the ISO-Uncia Leap Week Calendar and the Edwards perpetual calendar all use 30:30:31 days, the Symmetry010 Calendar uses 30:31:30 days and the Aristean Calendaruses31:30:30 days. When the “Thursday rule” is applied to any of these patterns it always results in a week layout of 4:5:4 as in the Symmetry454 Calendar, i.e. neither 5:4:4 as in the Bonavian Civil Calendar nor 4:4:5. Months of quarts, furthermore, cannot match exactly the full-week months determined by the week date ('-'''MM'-W'W or '-'Q'-'M'-W'W), because the first triad may have just 12 weeks and the third triad may also have 14 weeks (like the fourth). Quarts are therefore divided into three months that primarily consists of 4, 5 and 4 weeks ('-Q'Q'-'M'-W'W'-'D) and, matching that middle-high scheme, alternatively they consist of 30, 31 and 30 days ('-Q'Q'-'M'-'DD). Without weeks or days provided, i.e. in the form '-Q'Q'-'M, there is no distinction between these – the ''month duality. There is no way to reference a day in 28|35-day months without its week. Moon: 13 months * Alphanumeric dates * ‘M’ marker The week year is divided into 13 months, called moons. A normal moon has 4 complete weeks (28 days). The last moon in long years is a long moon and has 5 weeks (35 days). Since there is a leap week instead of intercalary days, these moons align with the week year, not the month year. This format is compatible with the New Earth Calendar and differs from the International Fixed Calendar (Cotsworth–Eastman plan), which uses intercalary days and starts weeks on Sunday. Mixed additions and clarifications Week of month or of triad * Alphanumeric dates * ‘W’ marker The number of weeks per month, hence triads, is determined by the usual Thursday rule, that means a week belongs to the month (or triad) the majority of its days (4 to 7) fall into, this always includes its Thursday. A short month has 4 weeks, a long month has 5 weeks. There are 4 long months in normal years and 5 ones in 53-week long years. The term normal month'is only used for Gregorian months of 28 to 31 days. A month has 5 weeks if it has at least 29 days and starts on Thursday, has at least 30 days and starts on Wednesday, or has 31 days and starts on Tuesday. The resulting pattern is irregular. The first triad may have just 12 weeks ('short triad), the second always has 13 weeks (normal triad) and either the third or the fourth may, instead of 13, have 14 weeks (long triad). Note that triads and normal months divided into full weeks together effectively constitute the week year and not the month year. To put it differently: every date with a ‘W’ marker in it uses the week year. Intercalary days * D = 0 is not the Sunday (7) of the preceding week, but is reserved for use for days outside the week cycle. * W'''WW = W00 is likewise intended for a week outside the month or quarter cycle. Financial and administrative additions '''this section is optional Fiscal quarters, months and year * Alphanumeric dates * ‘F’ marker Each of the 12 fiscal months has exactly 30 days, hence the fiscal year '''360 days. Each of the four '''fiscal quarters '''in a year by default has 90 days in it. All start and end dates, hence exact lengths, may be user-defined. The week is not used with this format! It is not (yet) defined how this fiscal year is mapped to a month year, because it would require intercalary days or flexible days longer than 24 hours. Optionally, though, month F00 and quarter F0 contain 5 days in common years and 6 days in leap years. Academic year, semester, trimester/term '''under contruction Astronomic and astrologic additions this section is optional Note that ±CCYY'L' and ±CCYY'S' are not the same. Lunar year and months * Alphanumeric dates * ‘L’ marker A lunar month or lunation has 29 or 30 days and is astronomically defined from new moon to new moon at 0° 0°. A day belongs to the lunation the majority of its hours belong to. Likewise, a lunar month belongs to the Gregorian year the majority of its days (15 to 30) fall into. The lunar year therefore contains either 12 or 13 complete lunar months. The week is not used with this format, but the ordinal days of the lunar month may be alternatively identified by being the n''th weekday of a kind in that month. Astronomic year and seasons, astrologic signs * Alphanumeric dates * ‘S’ marker Seasons (on the Northern hemisphere) and Western, tropical zodiac signs: “Taurus” for instance is “S12” or “S1-2” and neither “S02” (second sign in astrologic year) nor “S04” (fourth sign starting in a calendar year) nor “S05” (fifth sign in a calendar year). Only digits 0 through 4 are used with this format. It is not (yet) decided whether the seasons (and zodiacs) start at their traditional dates fixed in the Gregorian calendar (-03-21, -06-21, -09-23, -12-21 etc.) or are based upon accurate astronomic measurement or calculation. Time Allow decimal time of day without ‘T’ prefix: “.5” and “,5” mean 12:00:00. Allow decimal part with comma after century, year, week year, quart, triad, month, moon, week and, of course, day. Furthermore, allow spreadsheet-compatible date-times with day-count from 1900-01-01 epoch and dot divider: * D*'.d* — ., 1., .1, 1.1, 2., .2, 2.1, 1.2, 2.2 … * '''-'''D*.d* — -., -1., -.1, -1.1, … * '+'D*.d* — +., +1., +.1, +1.1, … Intervals, spans, periods, repetitions '''under contruction * ‘Q’ is added for the 13|14-week quart, 3-month triads remain “3M” * ‘F’ is added for the 30-day month (“30D”). * ‘L’ is added for the lunar month (ca. 29.5 days). It should only be used with absolute start or end date. * Complete dates, times and datetimes may be surrounded by paired parentheses ‘(’ and ‘)’. ** When start and end datetime in intervals are enclosed thusly the separating slash may be replaced by a double hyphen ‘--’ or en dash ‘–’. * Instead of the prefix marker ‘P’ or in addition to it, durations may be enclosed in paired square brackets ‘and ‘’. The opening bracket is placed before the marker if both are used. ** When the bracket notation is used, alternate symbols may be used for the year ‘a’, the month ‘mon’ and the minute ‘min’ and whitespace is permissable after symbols. * Instead of the prefix marker ‘R’ or in addition to it, repeated intervals may be enclosed in paired braces ‘{’ and ‘}’. The opening brace is placed after the marker, the optional number of repetitions and the slash, which also becomes optional then. Wildcards under construction When intervals are specified with start and end date and no duration, fields may be left out from the end date and are assumed to be the same as for the start date, e.g. 2012-09-10/11 is a two-day span. Alternatively, square brackets may be used around field values, which then can use a richer format: it contains a semicolon-separated list of spans where the end value and the slash are optional, e.g. 2012-09-10;12/14. The alternate double hyphen is also valid then, e.g. 2012-09-10--12. Brackets may be used with any field, e.g. 2012/2015-09-10. Uncertain dates, e.g. in genealogy, may be specified with a tilde followed by the amount of uncertainty, e.g. 2012-09-11~1 is the same as 2012-09-10--12. Another option to specify multiple or uncertain dates are wildcards. To mark a single digit as arbitrariy it is replaced by the marker ‘X’ (or ‘?’?), to mark a complete field – no matter its length – as arbitrary it is replaced by the marker asterisk ‘*’, but markers such as ‘W’ remain. In data interchange, digits to be filled in by the partner may be replaced by the underscore ‘_’ instead. Templates and comments under construction Comments Comments are placed between an opening angular bracket ‘<’ and a closing one ‘>’. A conforming software implementation may ignore anything after the comment start character and the matching comment end character or the end of the date string. Templates this section is optional Users may declare subdivisions of their own for the years defined above and they may specify dates in that custom calendar. *CCYY – 365|366 days, leap day, default *CCYY'W' = CCYY'M' = CCYY'Q' – 364|371 days, 52|53 weeks, leap week *CCYY'F' – 360 days, 12 months each 30 days *CCYY'L' – 12 or 13 month each 29 or 30 days *CCYY'S' – 4 seasons, 12 signs This is done by providing the length of the subdivision in angular brackets ‘<’ length ‘>’ after a slash ‘/’ and possibly the ordinal value before the slash. The smallest (and default) subdivision length before a ‘T’ marker is one day. If the subdivision length is the same for all items it is automatically repeated, otherwise alternating lengths can be separated by a colon to form a pattern, in the worst case a non-repeating pattern has to be used which lists all subdivision lengths. Separators, i.e. dashes, are not optional between closing and opening angular bracket. The leap item is indicated by an asterisk character ‘*’ followed by the number of items, which can be left out if equal to one ‘*1’. If there is an intercalary subdivision it is denoted by a plus sign ‘+’ and is either placed directly after the item it belongs to or after another slash. The hash character ‘#’ may be used in place of ordinal numbers when defining the calendar. In date designations, the ordinal number and the length must both be left-padded with zeros to the same length which must be the smallest number of decimal digits capable of representing the largest subdivision. Examples *Symmetry454 Calendar: **'Q'--- – the asterisk automatically is seven days, i.e. a week long, and is placed after the pattern has repeated four times **'Q'-- **'W'--- – since twelve items are needed, but the pattern only contains three, it is repeated four times **'W'-- *Symmetry010 Calendar: **'W'--<30:31:30> **'W'-- *World Season Calendar: **S-- **wrong: S--- – This way the second and fourth seasons had leap or extra weeks not days. *World Calendar: **-- – Simple form, but imprecise. **-- – More verbose form with the first month (and the week) made to start Sunday, intercalary days and leap days made special ‘@0’, which they are not by default. **wrong:-- – That would place an intercalary month and leap month after the twelfth, and both would have 31 days. *Pax Calendar: **W--- – Note how the leap week called “Pax” gets a month of its own and how it makes the pattern more complicated. The week starts Sunday ‘@7’. **W--- – Alternate, shorter form *International Fixed Calendar: **-- – Note how you cannot simply use 4 weeks, because of the leap day and the intercalary day which do not belong to any month. Weeks begin on Sunday, hence “/@7”, which also turns the two special days into virtual Sundays. **--- – Alternate, shorter form with special days made special ‘0’. *Gregorian Calendar: **-- – Note how the leap day belongs to February. Nothing is said about the week. Once a convention has been established, the lengths of the subdivisions may be left out. An epoch may be specified following the at character ‘@’ directly after the year, before any marker. There is no provision yet to specify a deviating leap rule. The first day of the week is Monday by default and a different weekday may be specified after an at sign right before the closing angular bracket for days. Holidays With a calendar reform there are always several ways to determine the date of annual holidays and birthdays. * Convert from the classic calendar each year, e.g. Christmas, December 25, stays at -12-25 and can fall on any day of the week. ** A special case are astronomically defined holidays which use features that are not accurately represented in the calendar, e.g. four days after the winter solstice (could be written -S0-1-04 or -S4-04 etc.). They have to be determined by observation or, rather, by independent calculation. * Convert the original date to the new calendar, e.g. 0000-12-25 was a Monday, hence -W52-1. * Use a similar looking date in the new calendar, e.g. -M12-25 which is a Thursday and equals -M12-W4-4. * Reinterpret the date in the new calendar, e.g. three weeks and four days into the last month of the year, -12-W3-4 (Thursday), or one week before the last day of the year, -W51-7 (Sunday). Depending on the reason for a holiday one or several of these methods may make sense to use. Note that stakeholders may prefer different approaches for external reasons, workers may prefer to have holidays not fall on weekends, for example. Astronomically defined holidays can of course be fixed arbitrarily in any calendar. The date of Easter in non-orthodox churches, for instance, is currently specified as the first Sunday after the first full moon after the begin of spring in the Gregorian calendar (-03-21). One could instead use the corresponding week from the year Jesus of Nazareth supposedly died on the cross, or one selects the day that is most frequently selected by the current rule or is closest to the median, -W14-7. Implementation under construction A fully compliant software implementation of this specification must be able to accept any of the formats described and convert it into every other representation. A partially compliant implementation must accept at least one of the formats and must not successfully parse any otherwise valid format into something else. Path syntax under construction In file systems and web addresses (URL, URI, IRI), the fields in hierarchical data are often separated by the forward slash or solidus ‘/’. In ISO 8601:2004, this character is used to separate the parts of time intervals instead. Formal grammar under construction Category:Leap Week Calendars Category:Proposed calendars Category:Equal-quarter calendars Category:28-35-day month calendars Category:30-31-day month calendars Category:28-day month calendars Category:13-month calendars Category:12-month calendars Category:Leap day calendars Category:Week starts Monday Category:Perpetual calendars